A teachers' union has pointed to deteriorating school buildings and worsening pupil behaviour for the numbers.
Teachers were much more likely to be injured in a science lab than in English class, it said.
In 2010, Te Puke High School students witnessed a 13-year-old classmate stab their maths teacher in the neck.
Steve Hose, 53, was rushed to hospital with four stab wounds but discharged that day.
National figures show the number of teacher workplace injuries has increased over the past three years, while the total cost to taxpayers dropped from almost $5.9 million in 2011 to $3.9 million last year, and $2.65 million this year to date.
Teachers have reported more than 5918 injuries this year - compared to 5457 for the whole of 2011 and 5669 for for 2012.
Teachers aged between 50 and 54 had the most injuries.
Soft tissue injuries were the most common, with more than 4000 reported each year.
Punctures, stings and lacerations were second, averaging about 650.
Fracture and dislocation injuries rose slightly, while the number of burns fell in the past two years. The number of dental injuries, concussions and "foreign bodies in orifices" was relatively stable.
Close to 4100 claims have been made by female teachers this year, costing almost $1.7 million - compared with 1810 male teacher claims, costing $886,000.
Post Primary Teachers Association president Angela Roberts said the national rise in injuries could be attributed to the deteriorating standards of school buildings and equipment.
"[The numbers] are a reflection of the increasing struggle that schools are having with maintaining ageing property.
"A lot of school buildings around the country are coming to the end of being fit for purpose and there is a massive issue around that."
Funds normally allocated for general maintenance had also been diverted for earthquake damage and leaky buildings, she said.
"You have holes in lino that people trip over, and you do have leaky roofs that make puddles that people slip in."
The rise of injuries could also reflect worsening student behaviour, and assaults on school staff, she said.
Increasing demands on teachers, including class sizes and workload also boosted stress levels.
Teachers were much more likely to injure themselves in the science lab than in English class, and increasingly complex timetables meant teachers were often lugging resources and equipment between classrooms, Ms Roberts said.